Help for Advanced Parol

I have applied for advanced parol, the INS receipt date is Sep,4,2003. I am applying for I-131 & I-485 together, I have not got the advanced parol yet. On the other hand, I am holding the air ticket to China on Dec,12. I have not been back for years. This really makes me nervous.
can anyone please tell me how long it will take to get it? Or, is that safe for me to be back first and ask my friend mail the document to me?
Thanks a lot!